A fuser included in an image forming apparatus includes a cylindrical fixing belt, a pressurized section arranged in contact with the fixing belt and including, for example, a pressurizing roller, and a nip forming section configured to press the fixing belt against the pressurized section and including, for example, a pressurizing pad. In the fuser, the nip forming section presses the fixing belt against the pressurized section to thereby form a nip portion between the nip forming section and the pressurized section. Thereafter, the fuser heats the fixing belt to desired temperature. After the temperature of the fixing belt reaches the desired temperature, when a sheet having a toner image formed thereon is conveyed to the nip portion, the nip portion fuses and presses the toner image and fixes the toner image on the sheet.
In the fuser, further improvement of fixing performance is desired. In order to improve the fixing performance, it is necessary to extend the nip portion in appearance to increase nip width. However, if the nip portion is extended, since an area of contact of the nip forming section with the fixing belt expands, the heat capacity of the fixing belt increases. Therefore, a long time is necessary from power-on of the image forming apparatus until the temperature of the fixing belt reaches the desired temperature.